Math:
Well, I know you don't want to go to the library, but... if you decide to go - and it is always a nice programme for me, as I love reading
- you can search for books written by two peruvian writers:
Manoel Scorza - he has some books witten about the fights between the poor "campesinos" against the owners of the land, which used to make them work for few money. One of his books has, at the last chapter, a nice description about a figh on the mountains between them: the first, using only slings; the others, firearms. It is a nice book.
Julio Ramón Ribeyro - on his "Complete works" , he wrote a story about a campesino boy who goes to Lima (The main Peruvian city), and everyone in the school, except a boy, laughs at him, as he uses to carry a sling - which represents, for the middle and upper classes from lima, in the book, a symbol of his poor origins.
If you want, try it - I am almost sure the books are translated to english.